package com.dongnam.security.auth.util;

import java.io.UnsupportedEncodingException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.PBEKeySpec;
import javax.crypto.spec.PBEParameterSpec;

import org.apache.commons.codec.binary.Base64;

/**
 * Basic symmetric encryption example
 */
public class CryptUtil {
    private static int ITERATIONS = 1024;
    private static final String password = "DFN#$WRIVBFOIEWQHqeoiruqwer23784fwjb";
    private static final String algothrim = "PBEWithMD5AndDES";
    private static final byte[] salt = new byte[] { (byte) 0x2c, (byte) 0x7a, (byte) 0x32, (byte) 0xf5, (byte) 0x08, (byte) 0xa9, (byte) 0xc0, (byte) 0xfe };    

    public static String encrypt(String plaintext) throws Exception {
        // Create the PBEKeySpec with the given password
        PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());

        // Get a SecretKeyFactory for PBEWithSHAAndTwofish
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(algothrim);

        // Create our key
        SecretKey key = keyFactory.generateSecret(keySpec);

        // Now create a parameter spec for our salt and iterations
        PBEParameterSpec paramSpec = new PBEParameterSpec(salt, ITERATIONS);

        // Create a cipher and initialize it for encrypting
        Cipher cipher = Cipher.getInstance(algothrim);
        cipher.init(Cipher.ENCRYPT_MODE, key, paramSpec);

        byte[] ciphertext = cipher.doFinal(plaintext.getBytes());

        String saltString = Base64.encodeBase64String(salt);
        String ciphertextString = Base64.encodeBase64String(ciphertext);
        
        return saltString + ciphertextString;
    }

    public static String decrypt(String text) throws Exception {
        // Below we split the text into salt and text strings.
        String salt = text.substring(0, 12);
        String ciphertext = text.substring(12, text.length());

        byte[] saltArray = Base64.decodeBase64(salt);
        byte[] ciphertextArray = Base64.decodeBase64(ciphertext);
        
        // Create the PBEKeySpec with the given password
        PBEKeySpec keySpec = new PBEKeySpec(password.toCharArray());

        // Get a SecretKeyFactory for PBEWithSHAAndTwofish
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("PBEWithMD5AndDES");

        // Create our key
        SecretKey key = keyFactory.generateSecret(keySpec);

        // Now create a parameter spec for our salt and iterations
        PBEParameterSpec paramSpec = new PBEParameterSpec(saltArray, ITERATIONS);

        // Create a cipher and initialize it for encrypting
        Cipher cipher = Cipher.getInstance("PBEWithMD5AndDES");
        cipher.init(Cipher.DECRYPT_MODE, key, paramSpec);

        // Perform the actual decryption
        byte[] plaintextArray = cipher.doFinal(ciphertextArray);

        return new String(plaintextArray);
    }

    public static boolean verify(String password, String encrypted) throws Exception {
    	if( CryptUtil.encrypt(password).equals(encrypted) ) {
    		return true;
    	}
    	return false;
    }
    
	private static String convertToHex(byte[] data) {
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < data.length; i++) {
        	int halfbyte = (data[i] >>> 4) & 0x0F;
        	int two_halfs = 0;
        	do {
	        	if ((0 <= halfbyte) && (halfbyte <= 9))
	                buf.append((char) ('0' + halfbyte));
	            else
	            	buf.append((char) ('a' + (halfbyte - 10)));
	        	halfbyte = data[i] & 0x0F;
        	} while(two_halfs++ < 1);
        }
        return buf.toString();
    }
 
	public static String MD5(String text) 
	throws NoSuchAlgorithmException, UnsupportedEncodingException  {
		MessageDigest md;
		md = MessageDigest.getInstance("MD5");
		byte[] md5hash = new byte[32];
		md.update(text.getBytes("iso-8859-1"), 0, text.length());
		md5hash = md.digest();
		return convertToHex(md5hash);
	}
}
